It is generally important when constructing a building to take insolation into consideration. For example, when a house is constructed in a country or region positioned on the northern side of the tropic of cancer, such as Japan, a technique of determining a target position of the house from a sun shadow position corresponding to the height of the sun at midday on the winter solstice, using heights of buildings located on adjacent land to the south side as a reference, may be employed conventionally (see JP 2003-167065 A (referred to hereafter as “Document 1”), for example).
Document 1 discloses a technique of determining an integrated sun shadow value by obtaining a sun shadow line formed at each hour in relation to a target site on which a house is to be constructed by a sunlight obstruction located adjacent to the site, and overlapping the sun shadow lines formed over a single day. In the technique described in Document 1, the object is to construct a house, and therefore a number of hours during which the sun shadow lines overlap on the winter solstice, when the solar elevation is lowest, is determined as the integrated sun shadow value.
Incidentally, a greenhouse is installed in order to cultivate a crop, and it is therefore necessary to learn an insolation amount over a period in which the target crop is cultivated. Hence, it is impossible to determine whether or not a planned location in which to install a greenhouse is suitable simply by determining the integrated sun shadow value of a single day.